1. Field of the Invention
This invention relates to the field of electromagnetic devices and more particularly to the field of instrument devices that require a constant high-density low-leakage permanent magnetic field and a force coil for operation such as dc meter movements, linear motors and some solenoids.
2. Description of Prior Art
Electromagnetic instruments such as dc meter movements typically employ a force coil supported on a bearing system and positioned in a magnetic field typically between the poles of a permanent magnet. Electromagnets are used in the prior art in place of the permanent magnets to provide a field having a flux density magnitude greater than that obtainable with permanent magnets. A field provided by an electro magnet requires a constant expenditure of electrical power to maintain the field.
Leakage magnetic flux, which is undesirable is unavoidably present with all these magnets, permanent as well as electromagnet.